a) Field of the Invention
The present invention relates to an instrument for the treatment of dental root-canals, comprising a tapered stem.
b) Description of the Prior Art
The treatment of a dental root-canal starts with the extraction of the nerve which is followed by rectification of the canal to open out the latter. This rectification is effected mainly by means of drills, of reamers, of cleansers and/or of files used some of them by hand, and others with mechanical driving means having a rotatable or a back-and-forth movement, or also a vibratory movement. The rectification of a canal is not effected by means of only one instrument but by means of the successive use of several reamers or files, starting with the smallest ones and ending with the biggest ones.
The rectification of curved root-canals raises problems so far as the instrument has a tendency to penetrate into the wall of the canal which is at the outside of the curve instead of following this curve up to the end of the dental root (apex).
Moreover, even if the instrument follows the canal up to its end, it has a tendency to act more strongly on the wall situated at the outside of the curve or to form thereon shoulders which will render more difficult the introduction of the next-used instruments up to the bottom of the root, and the subsequent obturation of the canal by means of gutta-percha points or cement.
This problem has been only partially solved by the utilization of very flexible instruments or of instruments with a non-cutting rounded point which is smooth or flattened, as well as by means of a pre-curving of the instruments.
However, the flexibility of the instrument does not always prevent the instrument entering into the wall of the canal nor ensure that it does not deform the canal by rectifying more strongly the wall of the canal on the outer side of the curve.
So far as the instruments having a rounded flattened and smooth point are concerned, they are in practice difficult to manufacture, especially when it is a matter of very fine instruments.